Polyvinyl alcohol (PVA) decomposes at 200.degree. C., well below the temperatures required for thermoplastic processing. In order to process PVA thermoplastically, it is necessary to incorporate plasticizers into the PVA resin to be processed. Plasticizers act to lower the softening temperature of PVA below the decomposition point.
Incorporation of plasticizer into the PVA resin has proven to be a challenge. The plasticizer must be in intimate contact with the PVA resin to assure a homogeneous melt upon processing. Granules of PVA which have been insufficiently permeated by plasticizer using known methods yield incompletely plasticized regions after thermoplastic processing. The art has addressed this difficulty by providing various means to absorb the plasticizer into the PVA resin. For example, plasticizer has been incorporated into PVA resin by the use of a liquid carrier which must be subsequently removed, requiring processing and drying steps. An alternate process requires heating and cooling of PVA resin in the presence of plasticizer. The resin particles absorb the plasticizer, swell, agglomerate, and are then mechanically separated prior to thermoplastic processing. Other processes require the presence of numerous solvents, substantial energy inputs, or long reaction times for the plasticization. Generally, currently known processes are intricate and/or require careful control of temperature in order to produce a homogeneous mixture of PVA and plasticizer.